/**
 * Copyright 2018 jianggujin (www.jianggujin.com).
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.jianggujin.codec;

/**
 * 字节数组与十六进制字符串互转
 * 
 * @author jianggujin
 *
 */
public class JHex {

   private static final char[] DIGITS_UPPER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D',
         'E', 'F' };

   public static byte[] decode(char[] data) {
      int len = data.length;
      if ((len & 0x01) != 0) {
         throw new IllegalArgumentException("Odd number of characters.");
      }
      byte[] out = new byte[len >> 1];
      // two characters form the hex value.
      for (int i = 0, j = 0; j < len; i++) {
         int f = toDigit(data[j], j) << 4;
         j++;
         f = f | toDigit(data[j], j);
         j++;
         out[i] = (byte) (f & 0xFF);
      }
      return out;
   }

   public static char[] encode(byte[] data) {
      return encode(data, DIGITS_UPPER);
   }

   private static char[] encode(byte[] data, char[] toDigits) {
      int l = data.length;
      char[] out = new char[l << 1];
      // two characters form the hex value.
      for (int i = 0, j = 0; i < l; i++) {
         out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
         out[j++] = toDigits[0x0F & data[i]];
      }
      return out;
   }

   public static String encodeString(byte[] data) {
      return new String(encode(data));
   }

   private static int toDigit(char ch, int index) {
      final int digit = Character.digit(ch, 16);
      if (digit == -1) {
         throw new IllegalArgumentException("Illegal hexadecimal character " + ch + " at index " + index);
      }
      return digit;
   }
}
